B-flavor tagging at Belle II

The European physical journal / C 82(4), 283 (2022). doi:10.1140/epjc/s10052-022-10180-9
We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom ( [inline-graphic not available: see fulltext]) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic [inline-graphic not available: see fulltext] decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of 62.8 fb$^{-1}$, collected at the resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be $\begin{aligned} \varepsilon _\mathrm{eff} = \big (30.0 \pm 1.2(\text {stat}) \pm 0.4(\text {syst})\big )\% \end{aligned}$for a category-based algorithm and $\begin{aligned} \varepsilon _\mathrm{eff} = \big (28.8 \pm 1.2(\text {stat}) \pm 0.4(\text {syst})\big )\% \end{aligned}$for a deep-learning-based algorithm.
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